[Structural mechanisms of interaction of cyanoacrylates with plant tubulin].

Structural mechanisms underlying the specific binding of cyanoacrylate compounds with tubulin of higher plants have been studied by example of interaction of ethyl-(2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and isopropyl-(2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA2) with Arabidopsis thaliana alpha-tubulin. It was revealed that the cyano group of cyanoacrylates is a functional analog of the nitrile group, which determines the processes of specific interaction with plant tubulin for dinitroaniline compounds. Based on the data of spatial structure fluctuations, dynamics of hydrogen bonds and interaction energy of the CA1 and CA2, the most probable binding mode for these compounds with plant alpha-tubulin was identified and appropriate site of interaction was characterized. Seven out of 10 residues composing this site (Gln-133, Asn-249, Val-250, Asp-251, Val-252, Asn-253 and Glu-254) are obligatory components of the dinitroanilines' binding site on the plant alpha-tubulin surface. Thus, the binding site on the alpha-tubulin surface characterized by us is able to recognize and specifically bind the substances which are cardinally different by their chemical nature and have no common pharmacophore groups, under the condition of a certain similarity of their electrostatic topology.

[Reconstruction of spatial structure of plant protein phosphatase type-1 and -2A in complex with okadaic acid].

The homology modeling, based on known temple structures of Homo sapiens protein phosphatase type-1 and -2A was implemented. The spatial structures of the human protein phosphatases and their plant homologs from Arabidopsis thaliana was predicted. The quality of models was confirmed by conformational analysis and root mean square deviations. The sites of okadaic acid binding in molecules of plant protein phosphatases (type-1 and -2A) were proved by the data of comparative analysis and molecular dynamics.

[Bioinformatic search of plant protein kinases, participating in microtubule protein phosphorylation and cell division regulation].

Bioinformatic search of plant homologues of human protein kinases SLK, PAK6, PAK7, MARK1, MAST2, TTBK1, TTBK2, AURKA, PLK1, PLK2 and PASK participating in microtubular protein phosphorylation and cell division regulation is carried out. The homologues of protein kinases SLK, MAST2 and AURKA were identified. It is found that closest homologue of human AURKA protein kinase is a protein with unknown function A7PY12_VITVI (STALK--Serine-Threonine Aurora-Like Kinase) from grape (Vitis vinifera). Reconstruction and analysis of three-dimensional structure of STALK protein confirmed its relation to the group of AURKA-like protein kinases.

[Structural-biological characteristics of tubulin interaction with dinitroanilines].

The interaction of dinitroaniline compounds with tubulin molecules is characterized by extraordinary selectivity--these matters effectively associate with plant as well as protozoan tubulin and practically don't interact with fungal and animal tubulin in spite of extraordinarily high level of similarity of their sequences. Structural features and mechanisms of this interaction are generalized and in detail analysed in this research. In particular, the regularities of dinitroaniline binding sites' structure and localization on surfaces of tubulin different subunits and tubulins of different origin are characterized. Dinitroaniline binding sites are disposed on the surfaces of longitudinal contacts between tubulin subunits, contain residues of diamine amino acids (lysine or arginine) coupling al nitrile group (s) of dinitroanilines. Binding site location on the surfaces of the same subunit of different origin (for example, plant and protozoan alpha-tubulins) is coincided, however site localisation on surface of alpha- and beta-subunits is distinct. The described sites potentially can be the binding areas for another antimicrotubular compounds, in particular, cyanoacrilates.

[Molecular and structural-biological analysis of Nicotiana plumbaginifolia mutants for identification of the site of beta-tubulins interaction with dinitroanilines and phosphorotioamidates].

The identification of point mutation locations on beta-tubulin molecules of amiprophosmethyl- and trifluralin-resistant Nicotiana plumbaginifolia lines have described in the work. It was shown that in the first case this mutation is connected with the substitution ofserine residue on proline in position 248; in the second case--with the substitution of phenilalanine on serine in position 317 of beta-tubulin amino acid sequence. Three-dimensional models of beta-tubulin molecule from Chlamydomonas with well-known location of mutations conferring dinitroaniline- and phosphorotioamidate resistance (substitution of lysine residue to methionine on position 350), and beta-tubulin from Nicotiana plumbaginifolia have been reconstructed. On the basis of analysis of site of interaction with dinitroanilines and phosphorotioamides on Chlamydomonas beta-tubulin molecule it was concluded that the revealed mutations on Nicotiana plumbaginifolia beta-tubulin affect amino acid residues participating in formation of this site.

[Bioinformatic search for plant homologs of Ste20-like serine/threonine protein kinases].

Eleven plant homologs of animal and yeast Ste20-like protein kinases were identified. It was shown that the nearest plant homologs of the Ste20-like protein kinases are the unknown proteins A9RVK0 from Physcomitrella patens ssp. patens and A7P2E2 from Vitis vinifera. Cladistic analysis showed a protein kinase dstl from Dictyostelium discoideum as the closest protein to the newly found plant homologs. A predicted spatial structure of the A9RVK0 from P. patens ssp. patens catalytic domain is presented.

[Construction of three-dimensional models of Arabidopsis thaliana FtsZ-proteins on basis of crystal structure of archaebacterial FtsZ-GDP complex].

Three-dimensional models of FtsZ-protein complexes with GDP from Arabidopsis thaliana L. localized in cytosol (Entrez database code NP190843) and in chloroplasts (Entrez database code AAA82068) were developed. Crystal structure of the FtsZ-GDP complex from archaea Methanococcus jannaschii (PDB-code 1FSZ) was used as a matrix. Secondary structures of computed models contain ten beta-strands. A chloroplast form of FtsZ-protein has ten alpha-helices and four 3(10)-helices, whereas cytosolic form of protein has nine and three structures correspondently and neither a0-helix before nucleotide-binding domain nor C-terminal 3(10)-helix in secondary domain. The T2-loop of nucleotide-binding pocket of chloroplast form of FtsZ-ptotein in position 111 contains non-charged alanin residue instead of the charged one which is typical for cytosolic and bacterial forms of proteins. At low sequence homology of FtsZ-proteins (approximately 47%) the developed models demonstrate high coincidence with matrix both in the structures of nucleotide-binding pocket and in the whole molecule. The models are completely suitable for further studies of possible sites of binding with dinitroaniline herbicides.

[Comparative analysis of primary structure of the mutant tubulins with resistance to antimicrotubular drugs for prediction of new mutations with analogous properties]. / Sravnitel'nyi analiz pervichnoi struktury mutantnykh tubulinov, ustoichivykh k antimikrotrubochkovym soedineniiam, dlia predskazaniia pozitsii novykh mutatsii s analogichnymi svoistvami.

All known for today complete amino acid sequences of alpha- and beta-tubulins were aligned and analyzed to reveal the regularity of location of mutations result in the resistance to antimicrotubular compounds and a prediction of positions of new similar mutations. It was shown, that known positions of amino acid changes lead to decrease a affinity to antimicrotubular agents with depolymerizing mechanism of action are consensus and located in proximity to the residues involved in intradimeric/interdimeric interactions and interactions with nucleotides (within of six residues), but never coincide with them. For changes lead to resistance to stabilizing antimicrotubular compounds, similar dependence is not traced. The identified regularity enables to predict the positions of new mutations lead to resistance to agents with depolymerizing mechanism of action.

[Analysis of structural characteristics of alpha-tubulins in plants with enhanced cold tolerance]. / Analiz strukturnykh osobennostei alfa-tubulina rastenii, obespechivaiushchikh povyshennuiu ustoichivost' k kholodu.

The uniqueness of the point substitutions in the sequences of two alpha-tubulin isotypes from psychrophilic alga Chloromonas that can determine the increased cold tolerance of this alga was analyzed. The comparison of all known amino acid sequences of plant alpha-tubulins enabled to ascertain that only M268-->V replacement is unique and may have a significant influence on spatial structure of plant alpha-tubulins. Modeling of molecular surfaces of alpha-tubulins from Chloromonas, Chalmydomonas reinhardtii and goose grass Eleusine indica showed that insertion of the amino acid replacement M268-->V into the sequence of goose grace tubulin led to the likening of this protein surface to the surface of native alpha-tubulin from Chloromonas. Alteration of local hydrophobic properties of alpha-tubulin molecular surface in interdimeric contact zone as a result of the mentioned replacement was shown that may play important role in increasing the level of cold resistance of microtubules. The crucial role of amino acid residue in 268 position for forming the interdimeric contact surface of alpha-tubulin molecule was revealed. The assumption is made about the importance of replacements at this position for plant tolerance to abiotic factors of different nature (cold, herbicides).